A pacer system normally includes a pulse generator located in a pacer housing, one or more leads and each having an electrode at the distal end thereof. The proximal end of each lead is connected to the pacer housing by means of a releasable connector. The connector includes a female connector part in the pacer housing. The proximal end of the lead normally is designed as a standardized male connector part and the female connector part normally is standardized to such an extent that it will receive this standardized male connector part. The most common way of fixing or locking the male connector part in the female connector part is to use set screws, which are oriented in an orthogonal direction in relation to the male connector part and which are accessible from the outside of the pacer housing. The female connector part normally is located in a header molded on to the housing.
Although these set screws generally have a good fixing effect, the screws are somewhat difficult to handle, the screws being small and easily lost, both during transport and storage and during implantation. For this reason, attempts have been made to develop fixing means, which more or less automatically lock the male connector part upon insertion thereof.
One device in which the proximal end of the lead is locked automatically is disclosed in U.S. Pat. No. 5,252,090. This device includes two elastically resilient metal tongues in a female connector part. The tongues are situated in a common plane and have a common central line, with a respective free end, which are located oppositely to each other. The distance between the two free ends is smaller than the diameter of the male connector part. The tongues will be deflected into the direction of insertion when the male connector part is inserted into the female connector part and the tongues thus will engage and lock the sides of the male connector part. If the male connector part is pulled outwardly from the female connector part, the locking effect will increase. This is because the friction between the tongues and the male connector part will draw the tongues in closer contact with the male connector part. The two tongues are integrally connected to two wings extending through openings in a header molded onto the housing. The wings are angled in relation to the plane of the tongues. Pressure on the wings will move the tongues out of engagement with the male connector part, which then can be removed.
In similarity with the design using set screws, the locking means in the above design have to be accessed laterally from the outside. For this reason, the locking means are located in the header in order to avoid openings for manipulation in the parts of the housing in which the electronic parts of the pacer are located. Any openings for the connections in the housing or can into the interior of the housing from the header thus can be permanently sealed.